Force-guided heuristic kinematics control of a continuum robot with variable curvatures

Continuum robots, particularly cable-driven continuum robots (CDCRs), have broad application prospects due to their lightweight and flexibility, featuring simple structures and actuation. However, their accurate control relies on high-precision kinematic models with nonuniform curvatures and the associate algorithms of inverse kinematics. In this article, the discrete elastic rod method based on discrete differential geometry is used to establish the variable curvature kinematic model of a CDCR, and a heuristic algorithm of optimal control guided by the virtual constraint forces are proposed to solve inverse kinematics efficiently. A closed-loop trajectory tracking controller based on the proposed algorithm is then designed with high tracking precision. Experimental results demonstrate that the dynamic deviation of the robot's free-end positions from the target ones under the condition of an acceleration 0.3 m/s2 is only 2.7 % of its total length, and it becomes 6.2 % even when the robot is carrying a payload of 100 g. The control error remains small at a tracking speed of 160 mm/s. Thus, the proposed force-guided heuristic algorithm provides a new way to construct effective dynamic controllers of continuum robots.